This invention relates to a system for indicating the operating state of a self-timer in an electric shutter camera exposure time control system using a digital recording and reproducing system for counting and memorizing a number of pulses produced from a pulse generator circuit in a counter circuit, said number corresponding to the brightness of a subject, and controlling the exposure time in response to the triggering of a camera shutter according to the memorized content of said counter.
Cameras provided with an electric self-timer system usually call for an indicator circuit for indicating the operation of the self-timer or the end of the self-timer operation because of the quiet operation of the self-timer of absence of a driven member driven in the operation of the self-timer such as a self-timer lever in a mechanical self-timer.
In the heretofore proposed systems for indicating the operation of an outside light detection type electric shutter, a delay circuit consisting of a capacitor and a resistor is provided separately of an exposure time control circuit so that it may be operated at the time of using the self-timer. Also, a self-timer operation indicator lamp is provided in parallel with a self-timer period control electromagnet, so that it is turned on when the electromagnet is energized. Further, at the end of the self-timer period the indicator lamp is turned off while de-energizing the self-timer period control electromagnet, thereby indicating the end of the self-timer period. Thereafter, a mechanical select switch is switched from the self-timer delay circuit to an exposure time control circuit while opening the shutter blades in a well-known method for the exposure. In another proposed system, a self-timer operation indicator circuit is connected in parallel with a self-timing delay circuit for indicating the self-timer operation by burning or on-off operating an indicator lamp during the operative period of the self-timer delay circuit. Then, at the end of the operative period of the self-timer a select switch is mechanically switched in response to the de-energization of a self-timer control electromagnet from the self-timer delay circuit including the self-timer operation indicator circuit over to an exposure time control circuit, while at the same time the shutter blades are opened for exposure.
For inside light detection type electric shutters, however, there has not heretofore been proposed an electric self-timer circuit either for the system where the exposure time is controlled in an analog manner or for the digital control system. Consequently, no associated indicator circuit has been proposed.
Ponderable systems for indicating the operation of an inside light detection type shutter self-timer may include one, which, like the afore-mentioned outside light detection type electric shutter self-timer operation indicator circuit, includes a self-timer delay circuit provided separately of an exposure time control circuit and operated at the time of using the self-timer. With such system, it may also be thought to provide a self-timer operation indicator lamp in parallel with a self-timer period control electromagnet and which is lighted upon energization of the electromagnet to thereby indicate the operation of the self-timer. Alternatively, an indicator lamp in a self-timer operation indicator circuit provided in parallel with a self-timer delay circuit may be lighted for indicating the self-timer operation.
In these systems, however, a self-timer delay circuit has to be provided separately of the exposure time control circuit. Particularly, a capacitor of a large capacitance is required to realize the self-timer period which is usually around 10 seconds, and this is disadvantageous from the standpoints of space factor and cost. Also, problems will be encountered in the reliability since use has to be made of mechanical select switches. Further, a decisive drawback of these systems is that it is difficult to obtain accurate memorizing operation in the inside light detection type electric shutter because the operation for indication is controlled by a signal from the self-timer control electromagnet. In other words, the time for memorizing the brightness of the subject is not available if it is so arranged as to turn off the indicator lamp and open the shutter blades in response to the de-energization of the self-timer control electromagnet at the end of the self-timer period. In case if it is so arranged as to effect the memorization within the self-timer period, the camera user cannot known when the memorization is effected since the electromagnet is energized during the self-timer period, with the indicator lamp being hence "on" during this period. Therefore, the indication of the self-timer operation in the proper sense, that is, indication or forecast of the end of the self-timer operation, cannot be obtained.